Television signal-translating apparatus



April 18, 1944. J 'A RADO TELEVISION SIGNAL-TRANSLATING APPARATUS FiledMarch 26, 1942 INVENTOR JOHN A. RADO BY y A'I'I'O NEY Patented Api# is,1944 TELEVISON-SIGNAL-TBANSLATING APPARATUS John A. Rado, Douglaston, N.Y., assigner to Hazeltine Corporation, a corporation of DelavaleApplication March 2s, roca senin No. 436,229 5 claims.. (ci. sis-14)This -invention relates generally to focusing systems and, moreparticularly, to focusing systems of a type adapted for use in atelevision signal-translating apparatus including a cathode-ray typesignal-translating device.

In televisioni signal-translating apparatus' of the cathode-ray type itis a common and necessary 'expedient to provide an arrangement for thepurpose of focusing the electron beam of the cathode-ray tube. 4Whileknown arrange-- ments are generally effective to focus the electron beamof such signal-translating devices for constant operating conditions,it'is found that the arrangements of the priori-art are not able tomaintain the focus of the electron beam substantiallyl cnstant forvarying or fluctuating' operating. conditions. This is especially trueof those arrangements in which both the `acceleratingelectrode systemand the beam-focusing system of the cathode-ray. device are energizedfrom a common power-supply circuit.v In general, the focus of theelectron beam `is determined by the energization of both of thesesystems and. hence, in the prior-art arrangements of the type underdiscussion, uctuations in the voltage of the common ysupply circuitwhich cause corresponding variations'in the energization of focus of theelectron beam.

both of these units tend undesirably to vary the Since variationsof theenergization of t e ac-' celerating electrode system tend to va y thefocus of the electron beam in one sense, while corresponding variationsof the energization of the beam-focusing system tend to -vary the focusof the beam in the opposite sense, there is a' tendency for thevariations to compensate one another. However, in known focusingarrangements the compensation isimp'erfect because a given voltagefluctuation of the commonv supply circuit' generally causes thevbeam-'accelerating electrode system and the lbeam-focusing system toeiect focus variations of -different magnitudes so that the beam iseifectively defocu'sed. Therefore, it is necessary in suchy prior-artarrangements to provide a manual adjustment in the beam-focusing systemso that, when there is :a

fluctuation in the voltage of the common supply t circuit whichthrowsthe' electron beam out of focus, the energization of the beam-focusingsystem may be adjusted to reestablish proper beam focus; Such means forcontrollingvthe focus of the electron beam is undesirable in that itrequires an additional manual control `and does not automaticallymaintain the beam in constant focus under all operating conditions.

vvoltage of, which is subject to fluctuations.

It is anobject of the invention, therefore, to

provide an improved beam-focusing system for a televisionsignal-translating device of the cathode-ray type which avoids one ormore of the above-mentioned disadvantages of the prior art.

It is a further object of the invention to provide an improvedbeam-focusing system for a television signal-transmitting apparatus ofthe cathodeeray type which maintains the focus of the electron beamsubstantially constant even though the voltage of the supplycircuit'ofthe apparatus tends to uctuate and tends thereby to vary thefocus of theelectron beam.'

In accordance with the present invention, a

'beam-focusing system for the device having a predeterminedvoltage-focus characteristic, and a common supply circuit for thesystems 'the A plurality of magnetic` focusing windings are in.- cludedin the focusing system, the number of turns in each of the windingsbeing. such that the voltage-focus characteristics of the electrodesystem and the beam focusing system -are so related that uctuations inthe voltage of the supply circuit cause the systems to effectsubstantially complementary variations in thefocus of the beam wherebythe focus of the beam is main=-4 tained substantially constant.

In accordance with a feature of this invention,

the focusing windings of a magnetic beamfocusing arrangement which havepredetermined current-focus characteristics areindividually energized byway -ofcircuit means having predetermined voltage-currentcharacteristics whereby the focusing system is causedA to haveapredetermined voltage-focus characteristic 'related to that oftheaccelerating electrode system of the cathoderay device.

For a better understanding of the present invention, together with otherand further objects thereof, reference is had to the followingdescription taken in connection with thev accompanying drawing, and itsscope will be pointed out in the appendedclaims.

In the accompanying drawing, the single gure is a circuit diagram.partially schematic, of .a

complete modulated-carrier signal receiverembodying a preferred form 'ofthe present invention.

Referring now more particularly Yto the drawing, there is illustrated atelevisionreceiver. of

the superheterodyne type including an antennav system I0, II connectedto a radio-frequency am plier I2 to which there is connected in cascadea plurality ,of signal-translating stages: namely, anoscillator-modulator I3, an intermediate-irequency amplifier I 4, adetector and A. V. C. supply I5, a video-frequency amplifier I6, and acathoderay signal-reproducing device I1. LA unidirectional voltage isderived from detector and A. V. C. Vsupply I5 and applied to one o rmore of the tubes of radio-frequency amplifier I2, oscillator-modulatorI3, and intermediate-frequency amplier IQ to controlthe amplificationoi' the signal-translating stages of the receiver and thereby maintainthe signal input to detector lilwithln a relatively narrow amplituderange forza wide range of received signal intensities. A scanning unitl-B which includes synchronizing-signal separating .2 I, to theradio-frequency amplifier I2, the oscilgenerated in the line-scanningand field-'scanning generators of unit amplifiers I9 and they areapplied to I8 and applied to the scanning I9', respectively, from whichthe scanning elements of the v cathode-ray signal-translating device I1toprolator-modulator t3, the video-frequency amplier y I6, the scanningunit I8, and-the line-scanning amplifier` I9. The accelerating electrodesystem which, as will be disclosed more fully hereinafter, is includedin the cathode-ray device I1, is energized from supply-circuit 20 by wayof conductor 22. Operating-:potentials are also applied from the supplycircuit 20l to the intermediate- Afrequency ampliiier I4, and to theheld-scanning but, preferably,

ampliiier I9' in a manner to be described hereinv after. The .supplycircuit 20, in turn, isvene'r-g gized by way'of av connection 23 fromany suitable source of power. The stages of elements I2-20 and 24 of thereceiver, as thus far described, may all be of conventional and wellknown construction so, that detailed illustrations and descriptionsthereof are deemed unnecessary herein.

Referring brieiiy, however, to the operation of the receiving system,television signals intercepted by the antenna circuit I0', I Iareselected and ainplifed in the radio-frequency' ampliiler I2 andsupplied to the oscillator-modulatcr i3 wherein they are converted intointermediate-frequency signals which, in turn, are selectively amplifiedin the intermediate-frequency amplifier yIt and The modulation`delivered to the detector I5. components of the signal are derived bythe de'- -tector I5 and are supplied to the video-frequency amplifier I6 wherein they are amplified and from which they are supplied in theusual manner to a brilliancy-control electrode of a cathode-ray tubeincluded in the cathode-ray signal-translating device I1. The intensityofthe electron beam in the cathode-ray device I1 is thus modulated o rcontrolled in accordance with the video-frequency voltages impressedupon the control electrode thereof in the usual manner.

The modulation `components from detector I5 are also supplied to thesynchronizing-signal separating apparatus included in unit I8 which, in

turn, separates the synchronizing-signal cornponents from thevideo-frequency components and applies these components to the'controlcirduce scanning elds, thereby to deilect the intenthe transmittedpicture. The A. V. C. control potential, derived from unit II' and'appliedto one or more tubes of the preceding stages, serves to maintainthe amplitude of the signal input to de tector I5 within a relativelynarrow range for a wide range of received signal amplitudes. Soundsignals accompanying the received television program are reproduced insound-signal reproduce: 24 in a conventional manner.

Referring more particularly to that portion of the receiver whichembodies the arrangement of the present invention for maintaining thefocus of the electron beam of the image-reproducing device I1 constant,it'may be seen that the repro-4 ducing device I1 comprises aconventional type of cathode-ray signal-reproducing tube 2! having a-naccelerating electrode system including an anode 26 for acceleratinganelectron beam in well-known manner. This electrode system has apredetermined. voltage-focus characteristic, whereby variations in theoperating potential applied thereto from supply circuit 20 causepredetermined variations in the focus' of the electron beam.'

'A beam-focusing system ofthe magnetic type is provided for focusing theelectron beam of cathode-ray tube-2 and comprises at least one aplurality of magnetic focusing windings having predeterminedcurrent-focus characteristics, whereby variations in the 'current'in thefocusing windings effect variations in the'focus of the scanning beam.Thus, a.A first focusing winding 28 and a second focusing winding 29 arecoaxlally positioned about the neck of tube 25'. As is to be presentlydescribed, the

`circuit means connecting'thefocusing windings with the common powersupply 2l has such a predetermined voltage-current characteristic andthe number of turns in the focusing windings is so selected that thefocusingsystem is caused to have a predetermined voltage-focuscharacteristie related to that system. O nly those device I1 'necessaryto a completeunderstanding of the present invention have been shown Theremaining elements thereof are conventional .and

of the accelerating electrode of well-known'constructio It will beunderstood that the excitation circuits of the severalsignal-translating stages I 2I6, I8, I 8 and I9', which are included inthe receiver, have predetermined .voltage-current characteristics andthat, in general, these characteristics willv not be the same. -That is.a given fluctuation in the voltage of the sulmly circuit 2U causeswidely different current variations in the excitation circuits of theseveral signal-translating stages. In, accordance with the presentinvention, the several beam-focusingwindings are connected to supplycircuit 20 by way of theV excitation' circuits of thosesignal-translating stages of the re'ceive'x` ,which have suchpre'determined voltage-current characteristics tlat thebeam-focusingsystem is' caused to have apredetermined voltage-focus.characteristic so re portions of the reproducingA .ply "circut 20,andwinding 29 is connected in serie/ s in the circuit for supplying auni-directional operating potential to the eld-scanning amplier I9" fromthe supply circuit 20.

In considering the operation ofthe arrangement just described, it willbe understood that the voltage of the supply circuit is subjecttoiiuctuations which vary the energization of both the acceleratingelectrode system and beamfocusing system of the receiver and tendthereby undesirably to vary theY focus of the electron beam. However,the voltage-current characteristic of the excitation circuit of theintermediatefrequency amplier lli is such that a voltage fluctuationinthe supply circuit 20 produces' a current change in the Winding 28which tends to over-compensate the' change effected on the focus of thebeam by the accelerating electrode system in lresponse to thatfluctuation of the supply-circuit voltage.v On the other hand, thevoltage-current characteristic of the excitation circuit of the scanningamplier I9' is such that the voltage uctuation of the supply'circuit 20produces acurrent change in Winding 29 which tends to undercompensatethe variation eected on the focus of the electron beam by theacceleratingelectrode system in response to that voltage fluctuation.,Further, the number. of turns in each of the windings 28 and 29 are sorelated that the focusing system is caused to effect variations on thefocus of the -beam which substantially compensate variations eiectedthereon by the accelerating electrode system whereby the focus of thebeam is maintained substantially constant for fluctuations of :voltageof the supply circuit 20.

Thus it may be ,seen that, inA accordance with l the present invention,means arev provided for connecting at least a portion, of thebeam-focusing system in series withjat least one of thesignal-translating stages of the receivers to causel the "focusingsystem to have a voltage-'focus characteristic so Z'related'to that ofthe accelerating electrode: system that' fluctuations in the voltage ofthesupplyc'ircuit cause the systems to effect substantiallycomplementary variations in the focus of the electron beam. In thepreferred embodiment, however, as illustrated in the drawing, aplurality of circuit means is provided for individually connecting theseveral windings of the focusing system with the common powersupplycircuit.

While in accordance with the specificembodiment of the inventiondisclosed in the drawing and described above, an intermediate-frequencyamplier and a scanning amplifier have been included in the arrangementfor connecting the .focusing windings to the supply circuit to cause thefocusing system to have a predetermined voltage-focus characteristicrelated to that of the accelerating electrode system, it is to beunderstood that the invention is not limited to such a combination.Obviously, others of the signal-translating stages included within thereceiver may be used in order to give the focusing system the requiredvoltage-focus characteristic.

manner: Connect a nrst winding of the beamfocusing system to the commonpower supply circuit by way of a circuit arrangement selectedfrom theexisting circuits of the receiver and having such a voltage-currentcharacteristic that the rst winding tends to overcor'npensat'evariations eiected on the focus of the beam by the acceleratingelectrode system in response to v'oltage fluctuations of the supplycircuit; connect another winding of the beam-focusing system to thesupply circuit by way of another circuit arrangement selected from theexisting circuits of the receiver and having such a voltage-currentcharacteristic that the second Winding tends to undercompensatevariations eiected on the focus of the beam by theaccelerating-electrode system; and proportion the number of turns ineach of the windings toobtain the total number of ampere turns requiredto focus the beam and to compensate exactly the changes effected on' thefocus of the beam by the accelerating electrode system.'

While it is not intended to limit the invention to any specific circuitarrangement or circuit constants, the following are suitable for use inan embodiment of the invention using the specific circuit illustrated inthe drawing:

Cathode-ray tube. Type 12AP4 Voltage of supply-circuit 2U (averagevalue)- 117 Operating potential of anode 2 6 (average Assuming that lthevoltage of the supply circuit 20 iiuctuates between 110 and 120 volts,the total number of ampere turns required properly to focus the beam atminimum and maximum values of the supply circuit voltage are 450 and550, respectively. The exciting current of the intermediate-frequencyamplifier Il has an average value of 50 milliamperes which variesbetween 40 and 60 milliamperes in response to the assumed voltagefluctuations of the supply circuit. The exciting current of theLem-scanning ampliiier I9' has an average value of 50 milliamperes whichvaries between 47.5 and 52.5 milliamperes in response to thedfoltagefluctuations of the. supply circuit. Kno'iving the ampere turns requiredproperly to focus the beam for the several values of supply-circuitvoltage and knowing the current in theexciting circuits of theampliiiers I4 and I9* for these values of supply-circuit voltage, it mayeasily be determined that winding 2a should comprise 3333 turns andwinding 29 should comprise 6667 turns. In such 'a circuit arrangement,the beam-accelerating electrode system and the beam-focusing system ofthe cathode-ray tube 25 eiect substantially complementary variations onthe focus of the electron beam in response to voltage fluctuations ofthe supply circuit 20 and thereby maintain the focus of the beamsubstantially constant.

While there has been described what i's at present considered to be thepreferred embodiment of pended claims to cover all such changes andmodiiications as fall-within the true spirit and scope oi' theinvention. V

What is claimed is:

1. A --televislon signal-translating apparatus comprising, a cathode-raysignal-translating device,A an accelerating electrode system for saiddevice having a predetermined voltage-focus characteristic, abeam-focusing system for said device, having a predeterminedvoltage-focus characteristic, avcommon supply circuit for said systemsthe voltage of which is subject to uctuations, and a plurality ofmagnetic focusing windings included in said focusing system, the numberoi' turns in each of said windings being such that the voltage-focuscharacteristics ofsaid electrode system and said beam-focusing systemare so related that fluctuations in the voltage of said supply circuitcause said systems to eilect substantially complementary variations onthe focus of said beam, whereby the focus of said beam is maintainedsubstantially constant.

2. A television signal-translating apparatus comprising, a cathode-raysignal-translating device, an accelerating electrode system for saiddevice having a predetermined voltage-focus characteristic, a`beam-focusing system for said device, a common supply circuit for-'saidsystems the voltage of which is subject to fluctuations, a plurality ofmagnetic-focusing windings in said focusing system having predeterminedcurrentfocus characteristics, and a plurality of circuit means havingpredetermined voltage-current characteristics .for individuallyconnecting each of said windings with said supply circuit, thevoltage-current characteristics of said circuit means and the number ofturns in each of said windings being suchthat said focusing system iscaused to have a voltage-focus characteristic so relatedl to that ofsaid electrode system that fluctuations in the voltage of said supplycircuit asians; @-5

cause said systems to effect substantially complementary variations inthe focus of said beam. 3. A television signal-translating apparatuscomprising, a cathode-ray signal-translating device, an acceleratingelectrode system for said deeach of said windings being such that saidfocusing system is caused to have a voltage-focus characteristic sorelated to that of said electrode sysi tem that fluctuations in thevoltage of said sull'-` ply circuit cause said systems to eifectsubstantially complementary variations in the 'focus of said beam. e, Ai l 4. A ltelevision Asignal-translating apparatus comprising, acathode-ray signal-translating device, an accelerating electrode systemfor said device having a' predetermined voltage-focus characteristic, abeam-focusing system for said device having a predetermined'voltage-focus characteristic, a common supplyl circuitfcr said systemsthe voltage of'which is subject to fluctuations, signal-translatingstages associatedv with said device having predetermined voltage-currentcharacteristics, and means for connecting at least a portion of saidfocusing system and at least one of said signal-translatingl stages inlseries with said supply circuit, the voltage-current characteristic ofsaid signal-translating stage being such that the voltage-focuscharacteristics of said electrode system and said focusing system arecaused `to be so related that uctuations in the voltage of said supplycircuit cause said systems to effect substantially complementaryvariations in the focus of said beam, whereby the focus of said f b'eamis maintained substantially constant.

5. A television signal-translating apparatus comprising, a cathode-raysignal-translating device, an accelerating electrode system for said'device having a predetermined voltage-focus characteristic, abeam-focusing system for said device, a= common supply circuit for saidsystems the voltage of which is subject to nuctuations, a pair ofmagnetic focusing windings in said focusing system having predeterminedcurrentli'ocus characteristics, a signal-translating stage associatedwith said device having'aA predeterv mined voltage-currentcharacteristic, scanning apparatus having a predeterminedvoltage-current characteristic for controlling a scanning 'operation ofsaid device, means for connecting said translating stage and one of said`windings in series with said supply circuit and for connecting saidscanning apparatus and the other of said lwindings in series with saidsupply circuit, the

voltage-current characteristics of said stage and said scanningapparatus and the number of turns in each of said windings being suchthat said focusing system is caused to have a 4voltage-focuscharacteristic so related to that of said electrode l,

system that iluctuations in the voltage of said supply circuit causesaid systems to effect substantially complementary variations in thefocus of said beam. v

JOHN A. RADO.

